Antisocial personality disorder (ASPD) is characterized by a persistent disregard for, and frequent violation of, other people's rights. The prevalence rate is 3 percent in males and only 1 percent in females. The disorder does seem to dissipate or burnout after the age of forty, which could be associated with hormonal changes at that age. ASPD is mostly comorbid with narcissistic personality disorder. Most etiology paradigms seem to imply a high interaction between the environment and genes for this disorder. Empirical evidence using adoption studies has found that regardless of genes, if an individual is raised in a highly stressful environment, he or she is still at great risk of developing ASPD. Neurobiological factors that may contribute to the onset and maintenance of this disorder are a weak behavioral inhibition system and an overactive reward system. The behavioral inhibition system is responsible for stopping behavior that may incur punishment. Psychopaths (people diagnosed with ASPD) tend to exhibit a type of habituation to punishment, wherein their physiological reaction to punishment is very weak. Psychopaths may also possess an overactive reward system wherein once there has been some reward in sight; even if the situation changes, they are unable to move away from the established goal.

Individuals with antisocial personality rarely seek professional help, and unfortunately, no form of treatment has been effective in treating this disorder.

Borderline personality disorder is characterized by marked impulsiveness and instability in mood, self-image, and interpersonal relationships. Manifestations of this disorder include frantic efforts to avoid real or imagined threats of abandonment, with opinions of significant others fluctuating between unrealistic positive and negative extremes. Individuals in this category tend to engage in para-suicidal behaviors such as cutting themselves. The hypothesis to explain these behaviors is that these types of acts help to break feelings of dissociation that these individuals usually experience. There are also high rates of suicide attempts in this category. The prevalence rate of borderline personality disorder is about 2 percent and 75 percent of the cases involve women. If the individual lines into his or her thirties, the symptoms tend to diminish, but about 60 percent of these individuals end their life in suicide. Borderline personality disorder is highly comorbid with histrionic and avoidant personality disorders. The disorder is called "borderline" because individuals in this category tend to be on the borderline between psychotic and neurotic disorders.

Family studies indicate that there may be a possible link between borderline personality disorder and mood disorders. There are also very high report rates of incidence of childhood physical and sexual abuse among people with this disorder, suggesting a possible specific link between these two factors. Although no disorder-specific drug has yet been found, a broad range of psychoactive drugs, ranging from antipsychotics and antidepressants to lithium and anticonvulsants, have been proven effective forms of treatment. Dialectical behavior therapy (DBT) has also been shown to be a promising treatment of borderline individuals. In this form of therapy, traditional behavioral and cognitive techniques such as problem- solving and skills training are used to maintain working interpersonal relationships and cope with stress, while the therapist concentrates on accepting the contradictory, demanding, and manipulative behaviors of the patient.

Histrionic personality disorder is characterized by excessive emotionality, overreaction to everything, and attention-seeking behavior. Individuals with this disorder are self-centered, vain, and demanding, and possess shallow emotions that fluctuate rapidly. The prevalence rate ranges from 2 to 3 percent and is higher in divorced or separated individuals. The disorder, which follows a chronic course, is highly comorbid with borderline and narcissistic personality disorders. One etiological explanation for this disorder comes from the psychoanalytic theory of parental seductiveness. Basically, this theory states that individuals who exhibit histrionic personality disorder had parents who chastised them for sexual behavior, while actually encouraging it at the same time. This led to conflicting signs concerning sexual indulgence, and subsequently to over- theatrical performances. Proof for this theory comes from the fact that the characteristic of emotional overreaction usually tends to have a sexual element or suggestion.

Narcissistic personality disorder is characterized by a grandiose view of self and an inability to empathize with others, for these individuals are preoccupied with their own achievements and abilities. This disorder is not chronic, and usually remits with time. Narcissistic personality disorder has a prevalence rate of about 1 percent. It is highly comorbid with histrionic and borderline personality disorders. One etiological explanation of this disorder can be found in the psychoanalytical area, which says that individuals suffering from narcissistic personality disorder tend to have a bi-polarity in their view of self, existing between two extremes: there is an idealized or over-idealized view of self, but this is combined with deep feelings of inferiority and low self-esteem. The grandiose image, then, is an attempt to cover feelings of inferiority. According to the proponents of this theory, since these individuals did not receive much encouragement and support from their parents during childhood, they tend to internalize the process by looking for these feelings within themselves.